Diesel engine with a pre-combustion chamber



Feb. 23, 1960 R. HERRMANN DIESEL ENGINE WITH A PRE-COMBUSTION CHAMBER Filed March 21, 1958 lum / NVE/v TOR ATTORNEYS DIESEL ENGINE WITH A PRE-COMBUSTION CHAMBER Rodolphe Herrmann, Le Vesinet, France, assigner to S ociete dExploitation des Materiels Hispano-Suiza, Bois- Colombes, France, a society of France Application March 21, 1958, Serial No. 723,001

Claims priority, application France March 21, 1957 11 Claims. (Cl. 123-32) This invention relates to vdiesel engines wherein fuel is injected into a spheroidal pre-combustion or vortex chamber which is connected with the corresponding cylinder by a so-called transfer passage. During the compression stroke air from the cylinder is forced under pressure into `the pre-combustion chamber and fuel is thereafter injected into a whirling mass of compressed air whereby the regularity of the combustion is enhanced.

In such an arrangement of pre-combustion chamber the axis of the transfer passage and the general center of the chamber determine a plane of symmetry which may be called the equatorial plane of the spheroidal chamber, while the planes perpendicular to this equatorial plane and which contain the center of the chamber are the meridian planes thereof. These meridian planes may conveniently be limited by the axis perpendicular to the equatorial plane and containing the center of the chamber in Such a manner that each meridian plane only intersects at a single point the protile of the cross section of the precombustion chamber in the equatorial plane thereof.

A iirst object of this invention is to provide an improved pre-combustion chamber arrangement which Ywill ensure a reduced fuel consumption of the engine and a more satisfactory operation thereof.

Another object of this invention is to provide an improved pre-combustion chamber arrangement wherein the so-called turbulent phenomena will be enhanced.

In accordance with this invention, in the equatorial plane of the pre-combustion chamber the mean radius of curvature of a irst portion of the profile of the said chamber which extends between the outlet of the injection nozzle and one edge of the transfer passage, is greater than the mean radius of curvature of the second portion of the said profile which extends between the outlet of the injection nozzle and the other edge of the transfer passage, and the said transfer passage opens into the precombustion chamber substantially tangentially with respect to the said first portion.

The equatorial plane of the pre-combustion chamber is preferably parallel to the axis of the cylinder. The transfer passage may conveniently be convergent towards the pre-combustion chamber and its transverse crosssection may be lenticular, its edge nearest to the center ofthe said chamber being in the form of a rounded transverse lip. The `surface of the wall of the precombustion chamber is preferably more or less flattened in the vicinity of the said lip to cause the whirling air to ilow regularly across the whole width of the lip.

IheV pre-combustion orvortex chamber may be conveniently realized by means -of a cavity provided in the cylinder head and of a. plug which is a force t in the opening of this cavity, the said plug being formed with the transferpassage. The plug may be at least partly heat-insulated with respect to the cylinder block in order to remain at a relatively high operating temperature for ensuring immediate ignitionV of the fuel and air mixture theinjectionperiod.

United States Patent O ffice ridian cross-,section as the point of intersection of this 2,925,807 Patented Feb. 23, 1960 In the annexed drawings:

Fig. l is a partial vertical cross-section of an engine provided with an improved pre-combustion chamber according to this invention, the plane of section being the equatorial plane of the chamber.

Fig. 2 is a plan view of the lower plug which forms a part of the precombustion chamber arrangement.

Fig. 3 is a section taken through the line III-, III of Fig. 1.

Fig. 4 diagrammatically shows a modification of the shape of the pre-combustion chamber shown by Fig. 1.

In the fragmental view of Fig. l, reference numeral 1 designates a'cylinder of an internal combustion engine of the diesel type, while 2 is the corresponding piston which has been illustrated at the end of the compression stroke.

The precombustion or vortex chamber 3 which corresponds to cylinder 1 communicates with the latter through a transfer passage 4. The fuel injection nozzle 5 opens into this precombustion chamber 3. As above explained the equatorial plane of chamber 3 is the plane of Fig. 1 which is determined by the axis of passage 4 and the center O of chamber 3, while the planes perpendicular to this equatorial plane (i.e. to the plane of Fig. 1) and which contain the said center O are meridian planes. These meridian planes may be conveniently regarded as extending outwardly from a line passing lthrough center O and perpendicular to the equatorial plane; i.e. the meridian planesl are terminated at the axis passing through the center O and are thus disposed about the axis in a manner similar to spokes on a wheel. The injection nozzle 5 is disposed in the equatorial plane which is a plane of symmetry for fthe pre-combustion chamber and the transfer passage.

The cylinder has been illustrated in the conventional manner with its axis vertical and with its upper end closed, the connecting rod and the crankshaft being disposed below the piston.

In accordance with this invention the profile of the cross-section of chamber 3 in the equatorial plane thereof, i.e. the curve shown in Fig. l, is such that the mean radius of curvature is greater in the upper arcuate portion comprised between nozzle 5 and the outer edgea of the `transfer passage 4, than in the lower arcuate portion comprised between nozzle 5 and the inner edge b of passage 4, and the outlet of the said transfer passage 4 linto chamber 3 is substantially tangential to the aforesaid upper arcuate portion of the profile of chamber 3 in the plane of Fig. l.

Although the radius of curvature could be caused to decrease progressively from point a to nozzle 5 and thereafter from nozzle 5 to point b (Fig. 4), in a preferred embodiment of this invention (Fig. l) the said radius is glven two successive predetermined Values respectively for the upper and for the lower portion of the equatorial profile' of chamber 3.

lIn the successive meridian planes, i.e. in the planes perpendicular to the plane of Figure l which extend outwardly from the axis passing through the center O and perpendicular to the equatorial plane, the radius of cur-` 3 Crass-.semina and Qf the equatorial Plane Comes nearer t0 oint b.

p The pre-combustion chamber nally obtained may be considered as formed of two substantially semifspherical halves, namely an upper half A having a radius R1 and a Acenter C1, and a lower half B with a radius R2 and a center C2, this second half becoming progressively attened towards the inner edge b of the transfer passage, in the form of a surface of revolution D with slightly curved generatrices. Fig. 2 shows the lines of level of this surface D and of the adjacent semi-spherical surface B, the dash and dot line approximatively indicating the zone where these surfaces merge into each other. Both centers C1 and C2 are substantially situated on the axis X-X of the injection nozzle and the general center O of chamber 3 considered as a whole is located between C1 and C2 as shown.

As above stated the radius R2 of the lower half B is smaller than the radius R1 of the upper half A. In actual practice R2 may be comprised between 0.65 and 0.85 R1.

The transfer passage 4 is preferably aring outwardly with respect to chamber 3 (i.e. converging towards the said chamber). Its transverse proiile is lenticular, as illustrated in Figs. 2 and 3, the greater axial width L thereof being perpendicular to the equatorial plane of Fig. l while its smaller axial width l is situated in the said plane.

The outlet of the transfer passage 4 is preferably perpendicular to the upper end 6 of the cylinder 1.

In such a case the flaring conformation of passage 4 may be obtained by disposing its outer wall 4a (i.e. the wall thereof which joins the upper portion A of the profile of chamber 3) substantially perpendicular to the upper end `6 of the cylinder 1 under consideration, while its inner wall 4b (Le. the wall thereof which joins the attened lower surface D) is slightly oblique, the angle of Obliquity being referenced a.

The junction between the outer wall 4a of passage 4 and the upper end 6 of cylinder 1 is preferably effected by means. of an intermediate portion 4c of substantially circular profile having a radius r as indicated in Fig. l.

The height or length of the transfer passage 4 is conveniently small with respect to the dimensions of the pre-combustion or vortex chamber 3. The rounded transverse lip 7 which limits the inner wall 4b of passage 4 is disposed at a height h above the end face of cylinder 1 which is at most equal to one half of the radius of curvature R1 of the upper half A of chamber 3.

The injection nozzle 5 is so disposed that its axis X-X is directed downwardly at a small angle of inclination (considered, of course, in the direction of the fuel jet) and that the said axis passes slightly above the abovedescribed lip 7 (angle in Fig. l).

The pre-combustion or vortex chamber 3 is realized in the conventional manner by means of a cavity provided in the cylinder head 8 and of a cup-shaped plug 9 fitted in the lower `or opening portion of this cavity the said plug being formed with the transfer passage 4. Plug 9 should be maintained at an elevated temperature during engine operation. For this purpose the pre-combustion chamber 3 may be disposed in part laterally with respect to cylinder 1, as indicated in Fig. l and the portion of plug 9 which extends outwardly with respect to the circular horizontal prole of cylinder- 1 is heat-insulated from the cylinder block 10 by means of a gasket 11 having a low heat conductivity, as for instance by means of an asbestos gasket.

The cavity of the cylinder head 8 and the corresponding plug 9 are each provided with two cylindrical fitting surfaces 12 and 13 having parallel but spaced axes in such a manner that the plug can only be disposed in the cavity at a single angular position. As illustrated in Figs. 1 and 2 these fitting surfaces 12 and 13 may correspond to two cylinders tangent to each other. Owing to their circular cross-section these surfaces are easily machined. It is besides to be noted that in actual practice only one of these surfaces needs being ground, preferably the outer surface 12.

As an example the dimensions for a given engine may be as follows:

R1=22.5 mm. R2; 17.0 mm. C1C2=R1-R2=5.5 mm.

L=30.0 mm. l= 12.0 mm. a=78 r=4.0 mm. h=10.0 mm.

=8 Angle of the conical fuel jet issuing from the injection nozzle=8 to 12.

During the compression stroke air from cylinder 1 is forced into the pre-combustion chamber 3 through the transfer passage 4, as indicated by the arrows in solid lines. The air stream sweeps the upper semi-spherical surface A and reaches the lower surface B where its angular speed increases, and it is deviated towards the general center of the pre-combustion chamber, as indicated by the arrows in dotted lines. The surface D causes the stream to flow regularly across the full width of the lip 7 which forms the inner upper edge of the transfer passage 4, as it will be appreciated by considering Fig. 2. Owing to this arrangement this air stream produces a ysuction effect on the air which ilows from cylinder 1 into chamber 3, whereby the said chamber is filled up to the possible.

It will besides be remarked that the air which enters the pre-combustion chamber during the compression stroke is constantly directed towards the lower plug 9 and thence toward the central zone of the chamber whereby wetting of the relatively cool upper wall A of the pre-combustion chamber is avoided.

When the fuel injection begins, the fuel jet 14 issuing fromr nozzle 5 is at once deviated downwardly towards the surfaces B and D of plug 9 under the action of the whirling air. There is thus obtained within the precombustion chamber a regime of high turbulence which results in an extremely homogeneous mixture of fuel and arr.

`During the compression stroke the transfer passage 4 acts as a convergent injector and it produces a high velocity air jet which enters tangentially the pre-combustion chamber towards the upper wall A thereof. During the expansion stroke passage 4 acts as a divergent nozzle whereby exhaust of the gases from chamber 3 into cylinder 1 is facilitated. The combustion gases are thus evenly distributed, the pressure on the working piston 2 is regular and the overall efliciency of the gas transfer is satisfactory- Qwing to the heat-insulation of plug 9, the exposed surfaces Bl and D thereof within chamber 3 remain at a relatively high temperature during engine operation. This ensures ignition of the fuel and air mixture notwithstanding the fact that the upper wall A of the precombustion chamber is cooled by the cooling water which circulates within the cylinder head 8 and by the incoming air during the compression stroke.

The improved precombustion chamber according to this invention affords a number of definite advantages with respect to the known dispositions. The fuel consumption is noticeably reduced; the torque is maintained at high engine speeds; the idling speed is lowered; starting 'remains easy even when the engine is abnormally cold.

I claim:

1. In an internal combustion engine of the diesel type a cylinder; a piston reciprocatable within said cylinder;

cylinder head mounted on said cylinder tofclose one endA thereof, said engine having formed therein externally of said cylinder a substantially spheroidal precombustion chamber having a center and a transfer passage with` an inner end opening into said chamber and an outer end opening into said cylinder to form a connection between said chamber and said cylinder, said transfer passage and said chamber having a common equatorial plane of symmetry; and a fuel injection nozzle mounted in said engine substantially in the equatorial plane lof said chamber and opening into said chamber, said nozzle being directed towards the inner end of said transfer passage; the mean radius of curvature of the cross-section of said chamber in said equatorial plane being greater in a first portion of said cross-section comprised between said nozzle and one edge of the inner end of said passage, than in the second portion of said cross-section' comprised between said nozzle and the other edge of said inner end, said transfer passage opening into said chamber substantially tangentially with respect to said first portion, and the cross-section of said chamber in successive meridian planes extending outwardly from the axis passing through said center and perpendicular to said equatorial plane having a radius of curvature substantially equal to the radius of curvature of the equatorial cross-section of said chamber at the point thereof where the latter intersects the meridian plane under consideration, except that the radius of curvature of the cross-section of said chamber in the meridian planes in the vicinity of said transfer passage increases as the point of intersection of the meridian planes and said equatorial plane approaches said transfer passage.

2. In an internal combustion engine of the diesel type a cylinder; a piston reciprocatable within said cylinder; a cylinder head mounted on said cylinder to close one Aend thereof, said engine externally of Asaid cylinder having formed therein a substantially spheroidal pre-combustion chamber and a transfer passage with an inner end opening into said chamber and an outer end opening into said cylinder to form a connection between said chamber and said cylinder, said transfer passage and said chamber having a common equatorial plane of symmetry; and a fuel injection nozzle mounted in said engine substantially in the equatorial plane of said chamber and opening into said chamber, said nozzle being directed towards the inner end of said transfer passage; the portion of the wall of said chamber situated on one side of a plane perpendicular to said equatorial plane and passing through the center of said chamber and through the inner end of said nozzle being substantially in the form of a first semi-spherical surface with said transfer passage opening substantially tangentially with respect to said first semispherical surface, and the remaining portion of the wall of said chamber comprising a second substantially semispherical surface adjacent said nozzle and having a smaller radius than said first semi-spherical surface, and a attened surface of revolution adjacent the inner end of said transfer passage.

3. In an engine as claimed in claim 2, the ratio of the radius of said second semi-spherical surface to the radius of said first semi-spherical surface being comprised between .65 and .85.

4. In an engine as claimed in claim 2, said transfer passage being convergent towards said pre-combustion chamber.

5. In an engine as claimed in claim 2, the length of said transfer passage being at most equal to one half of the radius of said iirst semi-spherical surface.

6. In an internal combustion engine of the diesel type a cylinder, a piston reciprocatable within said cylinder; a cylinder head mounted on said cylinder to close one end thereof, `said engine having formed therein externally of said cylinder ya substantially spheroidal pre-combustion `chamber and a transfer passage with an inner end opening into said chamber and an outer end opening into said cylinder, to form a connection between said chamberand said cylinder, said transfer passage and said chamberv having -a common equatorial plane of symmetry, and said transfer passage being of lenticular cross-section with the smaller width of said section situated in said equatorial plane, and said transfer passage opening into said chamber substantially tangentially to the inner Wall thereof; and a fuel injection nozzle mounted in said engine and having an inner end opening into said chamber substantially in the equatorial plane thereof, the axis of said nozzle passing substantially through the center of said chamber and being directed towards the inner end of said transfer passage; the inner wall of said chamber being divided into two portions by a plane perpendicular to said equatorial plane and passing through the center of said chamber and through the inner end of said nozzle, the portion farthest from said cylinder being substantially in the fonn of a first semi-spherical surface of constant radius, and the other portion -comprising a second substantially semi-spherical surface having a smaller radius than said first semi-spherical surface and situated adjacent the inner end of said nozzle, and a relatively flattened surface of revolution situated adjacent the inner end of said transfer passage and having its axis perpendicular to said equatorial plane and substantially passing through the center of said second semi-spherical surface, said surface of revolution being separated from said inner end by a rounded transverse lip.

7. In an engine as claimed in claim 6, the axis of said injection nozzle passing slightly above said transverse lip.

8. In an engine as claimed in claim 7, the profile of said transfer passage in said equatorial plane comprising a iirst edge perpendicular to the inner face of said cylinder head and substantially tangent to the proe of said precombustion chamber in said equatorial plane, and a second edge directed obliquely inthe direction of said rst edge from said cylinder to said chamber.

9. In an internal combustion engine of the diesel type a cylinder; a piston reciprocatable within said cylinder; a cylinder head mounted on said cylinder to close one end thereof, said engine having formed therein externally of said cylinder a cavity having a substantially spherical bottom and opening into said cylinder; a plug fitted in the opening of said cavity to determine within said engine a substantially spheroidal pre-combustion chamber, said plug having its side turned towards the bottom of said cavity in the form of a substantially semi-spherical surface with a smaller radius than the semi-spherical bottom of said cavity, and said plug being also formed with a transfer passage having an outer end opening into said cylinder and an inner end opening into said cavity substantially tangentially with respect to the semi-spherical bottom thereof; and an injection nozzle mounted in said engine substantially in the plane of symmetry of said cavity and of said transfer passage, and opening into said chamber, said nozzle being directed towards the inner end of said passage.

l0. In an internal combustion engine as claimed in claim 9, said plug and said cavity being each formed with two cylindrical surfaces having parallel but spaced axes and the cylindrical surfaces of said cavity being adapted to be tightly engaged by the cylindrical surfaces of said plug.

1l. In an internal combustion engine of the diesel type a cylinder, a piston reciprocatable within said cylinder, a cylinder head mounted on said cylinder to close one end thereof, said engine having formed therein externally of said cylinder a substantially spherodial pre-combustion chamber and a transfer passage with an inner end opening into said chamber and an outer end opening into said cylinder to form a connection between said chamber and said cylinder, said transfer passage and said chamber having Ia common equatorial plane of symmetry, and a fuel injection nozzle mounted in said engine substantially in the equatorial plane of said chamber and openins; ,Said chambers .said ner-ale being directed toward? the `inner 'end of said transfer passage, the mean radiu of curvature of the cross-section of said chamber in said equatorial piane'being greater in a first portion of said cross-section comprised between said nozzle and one edge of the inner end of said passage, than in the second portion of said cross-section comprised between said nozzel and the other edge of said inner end, said rst portion being substantially an arc of a circle of constant radius and said second portion being also substantially an arc of a circle of constant radius, the center of said rst portion being nearer to the inner end of said transfer passage than the center Aof said second portion and the general center of said chambery being situated between the center of said rst portion and the center of said secend, portion, said transfer passage on one sido substantially in line with the portion of the inner wall of said chamber where the-radius of curvature of said section ismaxirnum and making, onthe other side, an acute angle with the portion of the inner wall of said chamber Where the radiusof curvature offsaid section is` minimum.

References Cited in the tile of this patent UNITED STATES PATENTS 2,690,742 Kuepfer t Oot. 5,'-1954 FOREIGN PATENTS 837,643 France Nov. 18, 1938 885,142

France May 17', 1943 

